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What are the oxidation numbers for CrO4-2?
-1 for each F +2 for O
+4 for nitrogen
-2 for each O +6 for Cr
-2 for each O +6 for each Cr
Manganese oxidation number is +4 in MnO2
-2 for each O and +3 for N in NO2-
+6 for each Cr -2 for each O
+2 for Fe2+ ion
Oxygen has 6 valence electrons. It needs to gain two more to complete octet. So oxygen has an oxidation number of -2 when it gains 2 electrons (as in oxide ion)
Overall the anion has an oxidation number of -2, the same as its charge. The Cr is +6 and the O are all -2.
-2 for S in sulphides
C=x O= -2 (rule) (CO3)-2 has a charge of -2 x+ 3(-2)=-2 x=4 C=4 O=-2
Predominantly those in wide form periodic table column 16, especially oxygen and sulfur.
It can be a any group. Generally they shows +2 in group 2.
+7. The oxygen molecules (-2 each) have a total number of -16, therefore to get an overall charge of -2 each S atom needs to be +7.
As oxygen is a highly electronegative element, it tends to gain 2 electrons in most cases. The only exceptions are the peroxides, superoxides, ozonides and the oxy-fluoro co…mpounds.